Two-stroke internal-combustion engine



April 1953 A. STOLL 2,635,593

TWO-STROKE INTERNAL-COMBUSTION ENGINE Filed Sept. 19, 1949 2 SHEET$SHEET 1 INVENTOR ALBERT STOLL ATTORNEYS 5 P" 1, 1953 A. STOLL. 2,635,593

mo-s'mom INTERNAL-COMBUSTION ENGINE Filed Sept. 19, 1949 2 SHEETS-SHEET 2 W/l/I/l/I/I/I/l/l/l/l/b I ///I//////III////////// l V W INVENTOR ALBERT STOLL BY wax/ 9% AT TORNEYS Q. 'VUNITEDYVE STAT 'row of admission ports.

Patented Apr. 21,1953

TWO-STROKE Es PATENT OFFICE INTERNAL-COMBUSTION- ENGINE Albert Stoll, Augsburg, Germany, assignor to Maschinenfabrik Augsburg-Niirnberg A. G., Augsburg, Germany, a corporation of Germany Application September 19, 1949, Serial No. 116,433

V I This invention relates to a two stroke internal combustion engine with one-sided reversing scavenging by means of ports, of the type in which the exhaust ports are arranged above a internal combustionengines the attainable output depends in case of diesel engines on the weight of the air, or, in case of gasoline engines, on the weight of the gas-air mixture which is admitted into the working cylinder while the admission ports are uncovered. In case of two .stroke engines the charging of the cylinder causes particular difficulties since the admission of the fresh air or of the combustion mixture is closely connected with the removal ofv the exhaust gases from the cylinder. In this case not only a swift and perfect feeding of the new charge isrequired, but also a'corresponding removal of the waste gases. It is not possible simply to increase the cross section of the admission ports and possibly also of the exhaust ports, since this would result in a reduction of the effective piston stroke and so of the motoroutput. vAn increase of the admission ports only, at the expense of the exhaust ports, likewise would not bea remedy, since in this case the better feeding of the charge would be made illusory by a less efficient removal of the exhaust gas. Again, in case of an enlargement of the exhaust port cross section and a corresponding decrease of the admission port cross section the latter would become too small as to admit into the cylinder a suificiently large weight of charge during the available time. 4

It is also known that in two-stroke scavenging, more; particularly reversing scavenging a core (exhaustgas column) is resulting in the center of the cylinder, which core is not comprehended in the course of the flow of the scavenging air and which is diflicult to remove from the cylinder unless thecharacter of the scavenging is fundamentally altered. However, the complete and quick removal of this exhaust gas core is absolutelynecessary in order to charge the stroke volume with fresh air.

According to the invention this problem is solved by a special shape and direction of the single scavenging air jets, in such a manner that the height of the scavenging or admission air ports increases from the middle of the row of ports towards both ends, While the height of the exhaust ports decreases in the same direction. QThus, the port cross section available foreachkind of ports is not increased at the expenseof the other'kind of'ports, but it It is known that in" In Germany July 11, 1949 6Claims. (Cl.123 61) substantially only locally distributed in another manner. This distribution of the exhaust and admission ports takes place primarily according to the requirements of a swift and complete removal of the exhaust gases. The large exhaust cross sections in the middle of the row of ports permit a'very quick flowing off of' the bulk of the exhaust gases facing the middle ports in the middle of the cylinder, while the smaller lateral exhaust ports are perfectly sufficient for the substantially smaller quantities of exhaust gas at the sides of the cylinder. This favorable distribution of .the exhaust ports is primarily effective to prevent the formation of an exhaust gas core in the middle of the cylinder. Owin to the reduction of the cross section of the central admission ports with respect to the lateral admission ports the kinetic energyof the central scavenging currents is also reduced relatively to these exhaust gases towards the exhaust ports.

The scavenging of, the central space of the cylinder by the central scavenging currents is primarily caused by .the air currents issuing from the large lateral scavenging ports which currents advance with great energy between the opposite Wall of the cylinder .andthe scavenging air currents from the other admission ports and assist the erection of theseweaker air currents already before reaching the wall of the cylinder, so that the whole scavenging air current directed against the cover of the cylinder fills a substantially larger part of the cylinder volume. The rising scavenging air current is thus enlarged towards the axis of the cylinder, so to speak, so that the scavenging of the exhaust gas present in this central region is ensured.

In double-acting two-stroke engines the partition wall between the upper and lower air admission ducts or channels is advantageously not I passed to the cylinder wall, so that these chan- 'if the distanceb etween the cylinders shall not be in'creased.- Therefore, if both the channels of shown by way of illustration. and .not:by:wayof .1

limitation.

In the drawings:

Fig. 1 is the development of the portregion of a cylinder for a double acting two strokerensin 2 .is thedevelopment-of the port: region of ta;- cylinder-for; a singleacting.'twmstrokaengine,

.- Rig..- 3 is an axial sectionthroughethe. cylinder won line 13-13 oi-Fgig; 5,

Fig- 4 is an axial--sectionpthroughathe.cylin- Ider ofa-double-acting internalcombustion englue, in a perspective representation,

Fig.5 is-.a horizontal section through thecylinder. on lineA-A of Fig. 1. V

- Similar reference numerals denote similar'f parts in the difierent views.

Referring. now. .to. the drawings -.in greater. de-

- tail,.-and first to. Fig.1, it will-.be. seen that. the admission portsL. .II,. 111.3116.. IV. for. the upper and.- lower: .side of .the. cylinder .are .designed. in .sucha way .thatl..'their...height continuously increasing. also .wlthlnthe .sin'gle. ports. from. the middle .of the. row. of. ports towardsthe-sides.

.Similarlythe height of the exhaust ports. 2,. 3, 4

on. toputhereof is .decreasing. Therefore, the :barst oithecylinder wallbetweenthe admissionand .exhaust ports-.areslanting. Infthe embodiment as. per. Ztheeheight. of the ports is...changing .in. stepslfnom portto port. Depending. on the. flowingand feeding conditions. of the r v p and saidexhaust ports'beinglo-cated on the same charge...a..lower sadmission port. I may be ar- :Of 7 a. particular importance 5' for the "cylinder .charge arejthe lateral admission-ports V'which have. the maximum height of .all'admission ports f ...and' therefore are the first to. be uncovered and the last to. be covered by the piston. When they :are covered, a part of. the exhaust cross section is-also already coveredby thepi'ston. The course of. .the scavenging current'will' be seen fromFigs. 4 and 5. The last scavenging currents from the lateral. admission ports V owing to their increased kinetic energy will advance up to the ;rear wall of .the cylinderand erect each: other mutually. They form in front of thecylinder -wall a wallet/scavenging air at which the scavenging air currents fromthe smaller. admission ports are alsoerected and caused to..fi0w up- :wards towards .the: cylinder cover, seizing .the :centraltzone and thus; preventing the formation of an exhaust gascolumn.

It. is important for the filling of .the cylinders :of double-acting internal combustion engines Ethat the: two feed ducts -I 0- and I4. fontheup";

' nels.

per and lower side of the cylinder cooperate in such a manner that a larger charge is attained. This cooperation is attained by providing the partition Wall I 5 (Fig. 3) in such a manner that it does not go through to the cylinder wall as in 1 theother admission ports. :Thuslthe charge is 'permittedto. flew intomthe samezpart of the cylinder (upper or lower part) from both chan- This is particularly advantageous if owing to a small distance between the cylinders the'channels l0 and [4 have to be made small.

- It is also possible in case of single-acting internal. combustion engines to make the ports V -'1arger .in.-a downward direction than the other 15.

admissioni-portsif an increased charge can be attained thereby in view of the shape of the piston; or." of the feed ducts Ill, as the case may 'Whileithe invention has been described in detail with respect to certain now preferred examples. and .embodiments. of the invention itwill ..be...understood. by. those- .skilledin the. art: after understanding ilthe invention, .that various changes: and modifications may. be made withoutjdeparting from the. spirit. and scope of .the invention and it .is intended. therefore, -to..cover all such changes and modifications. .in. the appended claims.

'I-Iaving thus described my invention, I claim asnewand desire to secure by Letters Patent:

1.. In a two-stroke internal combustion engine with. one-sided reversing. scavenging, a cylinder having a row of admission ports and a row of exhaust ports, said admission'ports and said exhaust p'crts'being located on the same side of saidcylinder" and the height of said admission ports increasing from the middle of the row of ports" towards both ends, while the height of said exhaust ports decreases in the: same. direction.

2. In a two-stroke internal combustion engine with one-sided reversing scavenging, at

least one cylinder comprising a row of admission; ports, a'row of exhaust ports and'bars' between said rows of ports, said" admission'ports side-of the cylinder and said bars being inclined in such a way that the height 'of said" admission ports increasesfrom the middle of therow of 'ports towards both ends, while-the height of said exhaust ports decreases in the same direction.

"3. Ina two-stroke internal combustion engine with one-sided reversing scavenging, acylinder *havingarow'of admission ports, feed ducts leading to said admission ports, and a rcw of exhaust ports, said admission ports "and said exhaust ports being located 'on the same side -ofithecylinder and the height of said admission .port-s.increasing-from the-middle of the row of ports towards :both ends, while the height of said exhaust 'ports' decreases in'; the same direction, and the feed ducts for the two outer admission ports being directed so that their partialcharging currents are oppositely directed.

.4. In a two-stroke internal combustionengine with one-sided reversing scavenging, at least one cylinder comprisinga row of admission ports and arrow of exhaust-ports, said admission ports and said exhaust ports being located onthe same side 5. In a double-acting two-stroke internal combustion engine with one-sided reversing scavenging, at least one cylinder, an upper row of admission ports, a lower row of admission ports, an upper row of exhaust ports and a lower row of exhaust ports, upper and lower feed ducts leading to said admission ports, and partition walls between said feed ducts, the height of said admission ports increasing from the middle of the row of ports towards both ends, while the height of said exhaust ports decreases in the same direction, and the partition walls between the feed ducts leading to the extreme outer admission port terminating at a point before the cylinder wall, in such a way that the two companion upper and lower feed ducts open out into a common port extending at both sides of the transverse middle plane between said rows of ports.

6. In a two-stroke internal combustion engine with one-sided reversing scavenging, a cylinder having a row of admission ports and a row of exhaust ports, said admission ports and said exhaust ports being located on the same side of the 6 cylinder and the height of said admission ports increasing from the middle of the row of ports towards both ends, while the height of said exhaust ports decreases in the same direction and is reduced to zero above the two extreme outer admission ports having the maximum height.

ALBERT STOLL.

References Cited in the file of this patent UNITED STATES PATENTS 

